1. Field of the Invention
The present invention relates to a position detector for detecting relative positions of two objects, and a camera-shake compensation mechanism and an image capture apparatus, each of which utilizes the position detector.
2. Description of the Background Art
There are various types of position detectors for detecting relative positions of two objects (a linear encoder, for example).
In order to meet demands for smaller size, lower cost, lower power consumption and the like, it is preferable to employ a position detector of a magnetic type which uses a permanent magnet (a magnetic force generator) and a Hall effect device (a magnetic sensor), among the various types of position detectors.
However, a Hall effect device and a magnet, characteristics of which are apt to vary greatly according to temperature, are susceptible to ambient temperature. Hence, it is desired to suppress influences of ambient temperature upon a Hall effect device and a magnet in using a Hall effect device and a magnet.
As one solution to suppress such influences of ambient temperature, Japanese Patent Application No. 2001-91298 (which will hereinafter be referred to as “JP No. 2001-91298) suggests one technique. According to the technique suggested by JP No. 2001-91298, a quotient of output values of two Hall effect devices (magnetic sensors), or an output-value ratio between two Hall effect devices, is obtained as an output representing a position (which will be hereinafter referred to as a “position output”), to thereby compensate for influences of temperature.
In the meantime, in order to improve accuracy in position detection performed by the above-described magnetic position detector, it is desirable to take into account influences of variation among individual magnets (which will be hereinafter referred to as “piece-to-piece variation”). In other words, it is desirable to compensate for piece-to-piece variation of magnets.
In this regard, the technique suggested by JP No. 2001-91298 can compensate for influences of temperature relatively easily. However, the technique suggested by JP No. 2001-91298 would have difficulties in suppressing influences of piece-to-piece variation. More specifically, to merely obtain a quotient of output values of two Hall effect devices (magnetic sensors), or an output-value ratio between two Hall effect devices, as the position output, could not easily compensate for influences of piece-to-piece variation of magnets. Additionally, influences of piece-to-piece variation of magnets may be compensated for by previously preparing an adjustment parameter adapted to cancel piece-to-piece variation of magnets for each position detector, and adjusting sensitivity using the adjustment parameter. However, to prepare the adjustment parameter for each position detector is an extremely laborious process, which is almost impossible.